Controllable pitch propeller



Feb. 15, 1955 J. F. HAINES 2,702,086

CONTROLLABLE PITCH PROPELLER Filed June 18, 1955 6 Sheets-Sheet 2 3 INVENTOR. JOHN F. HA|NE S k -H661 85 BY 55' 0 10588 ATTORNEYS a Sheets-Sheet 6 J. F. HAINES CONTROLLABLE PITCH PROPELLER P II R N W l m mus; m3 m m N H CNN W m E N Y E B mwxEEzP mmN WMN 8 37 NOW 3-2102 m8 NW NE Feb. 15, 1955 Filed June 18, 1953 ATTORNEYS United States Patent 2,702,086 CONTROLLABLE Prrcn PROPELLER John F. Ha'iiies, Dayton, Ohio, a'ssign'or to McC-auley Industrial Corporation, Dayton, Ohio, a corporation of New York' Application June 18, 1953, Serial No. 362,587

9 Claims. (Cl. 170-16017) This invention relates to controllable pitch propellers for aircraft.

It is generally an object of the invention to provide a controllable pitch propeller capable of continuous control over a wide angular range including a fully feathered position, and more particularly to provide suchxa propeller wherein constant control of pitch with relation to desired'propeller speed isrefiected and maintained by a combined electric-hydraulic control system requiring comparatively little power beyond that of the engine itself.

A further object of the invention is to provide a controllable pitch propeller system in which governing of the pitch of the propeller blades is accomplished by comparing the rotational speed of the propeller with that of a master speed source and initiating blade pitch change in response to a difierence between these two speeds.

An additional object is to provide a controllable pitch hydraulic propeller in which the pump rotates with the hub and is driven by engagement with a magnetically responsive element which is subjected to an external magnetic field to retard its speed or to reverse its direction of rotation to thereby produce a driving action of thepump.

A further object is to provide such a controllable pitch propeller system which includes controls for selectively feathering and unfeathering of the blades through the main control mechanism by suitable regulation of the power supply.

It is also a major object of the invention to provide such a controllable pitch propeller system capable of adjusting the pitch of the propeller under control conditions such that the speed of the engine can be maintained within close limits over a wide speed range entirely without moving or rotating oil seals or collector -ring assemblies. 7

Still another object is to provide a controllable pitch propeller system which is applicable to a multi-propeller airplane, and which is eifective to control the pitch of the blades of all such propellers with relation to a rotating control field in such manner that all the propellers operate not only at the same speed but also in the same phase relationship.

In accordance with the invention, a desired reference speed for the propeller is established by means of a three-phase electromagnetic field rotating in a stationary housing within which the main control assembly is mounted for rotation with the propeller hub. This control assembly includes a synchronous rotor which follows this rotating field and which is free to rotate with respect to the control assembly structure so that a diiicrence between the propeller speed and control field speed results in rotation of the rotor with respect to the propeller structure. In the event of such relative rotation of the rotor and hub, a valve in the control assembly is operated to supply hydraulic pressure fluid to a double acting hydraulic cylinder in the proper direction to cause a correcting change of the propeller pitch, and the control assembly is so constructed and arranged that the resulting rate of pitch change is proportional to the phase dilference between the propeller and the control field.

The hydraulic pressure for effecting pitch control is supplied by a plurality of positive displacement pumps which are part of the control assembly and are carried withinand are rotatable with the hub. Operation of -the pum s is rovided by means or an electric induc- 2,702,086 Patented Feb. 15, 1955 tion coupling, or magnetically responsive element within the hub which is acted on by an external field to retard or reverse its rotation, and the control assembly also includes a self-contained reservoir of hydraulic fluid for the pumps. Normal governing control is obtained by using the output of only one pump, and the additional pump is utilized only for major pitch changes such as when it is desired to feather the blades. Un-

feathering is accomplished by impressing a difierent power supply on the pump drive coupling to drive the pump independently of the engine until the propeller starts to rotate by wind-milling. Thereafter the control system may be returned to normal in conjunction with starting of the engine.

It is accordingly among other objects of the invention to provide a controllable pitch propeller system wherein a magnetic element within the propeller hub is caused to rotate under the influence of a rotating electromagnetic field in stationary windings outside the hub, and wherein a control member responds to differences in speed between the field and the magnetic element to thereby regulate a power drive for eifecting adjustment in the pitch angle of the propeller blades.

An additional object is to provide such a controllable pitch propeller system in which the speed of rotation of the control field for a magnetic element within the propeller hub can be adjusted as desired to actuate the magnetic control element within the hub and thereby to establish a different pitch and speed of the propeller.

It is also an object of the invention to provide a controllable pitch propeller system in which a pump carried by the propeller hub develops hydraulic power for the adjusting mechanism for the propeller blades and in which the pump is in turn actuated and controlled through an electric coupling from an electromagnetic field located outside the propeller hub.

Still further objects and advantages of the invention will be apparent from the following description, the accompanying drawings and the appended claims.

In the drawings- Fig. l is a view in front elevation, partly broken away, showing a controllable pitch propeller system constructed in accordance with the invention;

Fig. 2 is an enlarged side elevational view looking from right to left in Fig. l and partly in section on the line 2-2 of Fig. l; 1 Figz. 3 is a fragmentary section on the line 33 of Fig. 4 is an enlarged fragmentary section on the line 44 of Fig. 1;

Fig. 5 is a transverse section on the line 5--5 of Fig. 8 and also of Fig. 2;

6 is a fragmentary section on the line 66 of 7 is a fragmentary section on the line 77 of 1g.

Fig. 8 is a section on the line 8- -8 of Fig. 5;

Fig. 9 is a section on the line 9--9 of Fig. 5;

10 is a section on the line 1010 of Figs. 2 an i Fig. 11. is a schematic view of the hydraulic system of Figs. ll0;

Figs. 12 and 13 are wiring diagrams; and

Fig. 14 is a diagrammatic view illustrating the application of theinventimi to a multi-propeller airplane.

Referring to the drawings, which illustrate a preferred embodiment of the invention, the propeller hub indicated generally at 20 includes sockets 21 within which are mounted the shanks of the two blades 22. A split sleeve 23 is clamped to the shank of each blade and is mounted within the socket 21 by means of the retaining nut 24 and the bearings indicated generally at 25, thus providing a rotational mounting for adjustment of the pitch angle of the blade.

Rotation of the blade root for pitch adjustment is effected and controlled by means of a gearsegment 30 which is bolted on the inner end of the sleeve 23 and meshes with rack teeth '31 on the rod 32 of an annular piston 33 in an annular cylinder 35 formed by inner and outer walls 36 and 37 mounted on the front of the hub 20. Hydraulic fluid for movement of piston 33 is supplied and controlled by the control assembly which is an annular unit mounted behind the propeller hub and surrounding the propeller shaft (not shown).

The control assembly is shown in detail in Figs. 5-10, and it includes stationary parts mounted on the engine and rotating parts carried by the propeller hub. Referring particularly to Figs. 8 and 9, the stationary portions of the control assembly include a. plate bolted to the engine or fuselage at 41 and a housing 42 bolted to plate 40 and supporting a pair of stators 44 and 45 hav ng three-phase windings 44a and 45a for the pump drive rotor and control rotor respectively. A spacer r 1ng 46 separates these two stators, and an entering opening for the electric leads to the stators is indicated at 47 in housing 42.

The rotary portion of the control assembly 1ncludes a pair of end plates 50 and 51 which cooperate with a thin walled cylinder 52, a spacer sleeve 53 and O-rings 54 to define an annular chamber which forms the reservoir 55 for hydraulic fluid for cylinder 35. These parts are secured together by a plurality of bolts 56, alternate ones of which are extended to secure these different units directly to the propeller hub. This whole unit is therefore free to rotate with the propeller hub and with respect to the housing 42, and there is accordlngly a small radial air gap between the wall 52 and the stators 44 and 45 for such rotation. The wall 52 is formed of thin stainless steel or other suitable nonmagnetic material of relatively high internal resistance to keep eddy current losses at a low value.

The hydraulic fluid from the reservolr 55 is supplied under pressure to the cylinder 35 by a pump unit indicated generally at which is mounted on the front of the end plate 50 and includes a base plate 61, a pump body 62 and a cap 63. Within the pump body is a pair of gear pumps 65 and 66 on shafts 67 and 68. The gears of these pumps are shown as of the same diameter but of different widths and thus provide respectively a high pressure low rate pump 65 and a lower pressure high rate pump 66, as is indicated diagrammatically in Fig. 11 by showing the pump gears 65 of smaller diameter than pump gears 66. Both pumps are driven from the same common drive shaft 70 mounted by a bushing 71 In end plate 50 and including a pinion 72. The pinion 72 meshes with a ring gear 73 on the pump drive rotor 75, which is mounted by bushings 76 for rotation on spacer sleeve 53 between the end plates 50 and 51 and which carries the magnetically responsive element 77, comprising a series of laminations 78 with a squirrel cage or short circuiting winding 79 for cooperation with the pump drive stator 44.

The inlet for the pump unit 60 includes an inlet tube 80 mounted by a pivot screw 81 on the end plate 50 and connecting at 82 with a mating bore in the pump base plate 61. The lower end of the inlet tube 80 rests on a dowel pin 83 projecting from a boss portion of the end I plate 50 to maintain the inlet tube out of contact with the control rotor 85, which is mounted for rotation on the end plate 50 in cooperation with the stator 45. The control rotor 85 is held on end plate 50 by keepers 86 and 87, and its outer periphery is notched and carries an induction grid 88.

The output of the two gear pumps 65 and 66 is controlled by a selector valve indicated generally at 90,

which includes a sleeve 91 and shiftable spool 92 housed in a portion of the pump base plate 61. A fitting 93 connects the valve to a tube 95 secured at approximately its midpoint to the end plate 50 by a clip 96, and valve 90 is also provided with a drain line 99 (Fig. 11) to the reservoir 55. Shifting of spool 92 is effected by a bellcrank 100 pivoted to end plate 50 and including an arm 101 carrying a pin 102 engaging in a slot 103 in spool 92. The other arm 105 of bellcrank 100 is biased by a torsion spring 106 in clockwise direction as viewed in Fig. 5, and this arm 105 projects into the path of an operating nose 110 bolted to the control rotor 85, which also carries a similarly shaped counterweight 111.

In the normal position of valve spool 92 as determined by spring 106, the output of high pressure pump 65 is supplied to the tube 95, while the output of low pressure pump 66 is returned to the reservoir through drain pipe 99, as shown diagrammatically in Fig. 11. When valve 92 is shifted against spring 106, it closes the drain line 99 and adds the output of pump 66 to that of pump 65. In addition, when the drain line 99 is closed, the output of pump 66 is supplied to a hydraulically operated high pitch stop for the propeller. The stop 115 is shown diagrammatically in Fig. 11 as comprising a cylinder having its piston rod 116 normally projecting into the path of a shoulder 117 on the rack piston rod 32, and when the piston rod 116 is withdrawn from the path of shoulder 117, it becomes possible for piston rod 32 to move through a sufficient distance for full feathering of the propeller blade.

The discharge end of the tube 95 is connected by a second fitting 93 with the pitch control valve 120, which is housed with a pressure relief valve 121 in a common valve block 122 mounted on the front of the end plate 50. The pitch control valve is provided with pressure connections 123 and 124 with the two ends of the cylinder 35 to supply pressure fluid thereto for increasing and decreasing pitch respectively, and it is also provided with a drain connection 125 to the reservoir 55. The relief valve 121 is equipped with a spring 126 and closure plug 127, and it opens a drain connection 128 to the reservoir 55 when the pressure of spring 126 is exceeded.

The pitch control valve 120 is operated by the control rotor 85 through a cam 130 which is bolted to rotor 85 and includes an arcuate cam slot 131 having its center eccentrically located with respect to the center of the control rotor. Cam slot 131 receives a cam follower pin 132 on one arm 133 of a bellcrank 135 extending through end plate 50 into valve block 122. The other arm 136 of bellcrank 135 carries a pin 137 which projects into a slot 138 in the valve spool 140 to move this spool back and forth within the valve sleeve 141. This design of this assembly, including the electrical elements thereof, is such that when rotor 85 is rotating in synchronism and proper phase relation with the propeller, the valve spool 140 w1ll be held in neutral position corresponding to the centered position of pin 132 in slot 131, but whenever the propeller leads or lags behind the control field in stator 45, valve spool 140 will be shifted to supply pressure fluid to the proper side of cylinder 35 to increase or decrease pitch respectively, thereby correcting the speed of the propeller so that it accurately matches the speed of the control field.

Fig. 12 illustrates a wiring diagram for operation of the control system as described in connection with Figs. 1 to 11. A D. C. power supply is represented by the lines L1 and L2 provided with a main switch 150, and It provides power for operation of a motor 151 driving an A. C. generator 152 through a coupling indicated at 153. The generator 152 in turn provides the A. C. control field for the control stator 45 as determined by the speed control for motor 151 indicated at 155. 1363111311011 of the control system for normal operation 1s initiated by closing the pushbutton switch to energlze relay 161 through the normally closed contacts 162 of relay 163. Closing of relay 161 completes a hold-in c rcuit for itself through its back contacts 164, and a slgnal light 165 indicates when this relay is closed. At the same time relay 161 closes its contacts 166 to apply the A. C. field from generator 152 to control stator 45, and it also closes contacts 167 to apply a D. C. field through the resistor 168 to the pump stator 44. This results in retarding the rotation of the pump rotor, the field being so regulated that the rotor has approximately a 50 percent slip relative to the rotation of the hub.

Under these normal operating conditions, so long as the control rotor 85 and the propeller rotate in synchromsm with the control field in stator 45, the pitch of the propeller will be unchanged. If, however, the propeller should lag behind the control field, there will be relative movement of cam follower 132 in cam slot 131 which W11]. result in shifting of valve 120 in the direction to supply pressure fluid to the proper side of cylinder 35 to decrease the pitch of the propeller causing its speed to lncrease unt1l synchronization is again established. Similarly 1f the propeller should lead the control field, there W111 be movement in the opposite direction between the cam follower and the cam slot to cause shifting of valve 120 m the proper direction to supply pressure fluid to the other side of cylinder 35 and thus to increase the pitch of the propeller. During all such normal operating condit1ons, the D. C. field on the pump stator 44 will have a suflicient braking eflect on the pump drive rotor 75 to cause relative rotation of the pump drive gear 73 and plnlon 72 in order to maintain a supply of pressure fluid from the high pressure pump 65 as described, the output of the low pressure pu'mp- 66 being merely returned to complete a hold-in circuit around switch 170. The cam 172 momentarily closes switch 175 to energize relay 176 and also to energize relay 163 through the normally closed back contacts 177 of a relay 180, and closing of relay 163 completes a hold-in circuit through its contacts 181 for itself andrelay 176.

2 Closing of relay 163 causes its switch contacts 162 to open and thus deenergizes relay 161 to discontinue the D. C. field on pump stator 44 and the A C. field on control stator 45 by opening its contacts 167 and 166, but at the same time relay 163 closes its contacts 182 to apply a reverse A. C. field to the control stator and thus to retard and fully displace the control rotor 85 with respect to the propeller hub. This action overcomes the normal tendency of the system to decrease pitch in response to slowing down of the propeller and also positively drives the control rotor in counterclockwise direction as viewed in Fig. 5 until the nose 110 engages and operates the bellcrank 100. Similarly, closing of relay 176 causes its contacts 183 to close to apply an A. C. field on pump stator 44, the direction of rotation of such field being the reverse of the direction of rotation of the propeller so that even though the propeller may be turning rather slowly, a positive drive with an adequate speed of operation of the pump rotor will beprovided.

The resulting shiftingof valve 90 adds the output of the pump 66 to that of pump 6 5,to supply the maximum flow of pressure fluid to the cylinder 35, and since the driven movement of control rotor 85 also shifts valve 120 to its increase pitch position, this flow will be correspondingly delivered to the proper end of cylinder 35 to move the blades: towards maiiimum pitch or feathered position. At the same time, the output of pump 66 will also be delivered to the high pitch stop cylinder 115 to withdraw its piston rod 116 out ,of the path of the shoulder 117,- thereby permitting the blade to shift to fully feathered position. This entire operation continues only for the short interval established by the timer 171, which need be only of the order of 10' to seconds, after which cam 173 will permit switch 174 to reopen. This will deenergize both. of relays 1'63 and; 176, thus shutting off the power supply to both of stators 75 and 85 and bringing the systern to a complete stop with the propeller blades in feathered position.

Unfeathering of the propeller is initiated by closing the pushbutton switch 185, which must be held closed manually unless a timer is provided. This energizes relay 180 andreesta'blishe's through its contacts 186 an energ'izing circuit for relay I61. Closing of relay 161 reapplies theA. C.- field to control stator 45, but the D. C. field on the pump stator remains discontinued owing to the opening of contact 187 of relay 180. At the same time, however,- contacts 188 ofrelay 180 establish an energizing circuit for relay 176 which closes its contacts 183 and thus again applies a' reverse A. C. field to the pump stator 44. Since the propeller is still stationary, the pumps will be positively driven in the normal direction to supply the desired pressure fluid, and the control rotor will also be positively driven, in clockwise direction as viewed in Fig. 5, to shift valve 120 in the direction to deliver the fluid to the rearward end of cylinder 35 and thus to move the p'ropellerout of feathered position. This actionneed continue only for a sufficient interval to shift the blade out of fully feathered position, after which the propeller will start to rotate by wind-milling. The i switch 185 can then be released to open relay 180, thereby opening relay 176 and discontinuing the A. C. field to the pump stator, but since at the same time the switch contacts 187 will close, the normal D. C. field will be reapplied to the pump stator, thus reestablishing normal operating conditions.

Fig. 13 illustrates a modified wiring diagram for the control system in which a combination of A. C. and D. C.

power is used forfeathering, certain of the elements in this diagram corresponding with those in Fig. 12 and being provided with similar reference characters. Normal operation is initiated .byclos in'g' the pushbutton switch 160 to close relay 200, thereby also completing a holdmg the s ignal lam'p 202. Closing of relay" 200 closes its contacts 203 to apply the A. C. field from generator 152 to the control stator 45, and it also completes an energiz- In'g circuit for the relay 205 through the normally closed back contacts 206 of a relay 207. Closing of relay 205 closes its contacts 208 to apply the normal D. C. field through resistor 209 to the pump stator 44. This establishes the same normal operating conditions for the congol slstem as previously described in connection with Feathering with the system of Fig. 13 is initiated hy closing the pushbutton switch 170' to energize the timer motor 210 driving cam's 211,- 212 and 213, and the cam 211 immediately closes the switch 174 to complete a holdin circuit around switch 170 which may then be released. At the same time, switch 174 completes an energizing circuit through the back contacts 214 of relay 207 to a relay 215 causing it to open its' contacts 216 in the energizing circuit of relay 200. The resulting opening of relay 200 opens its contacts 203 to discontinue the normal A. C. field to the control stator, and also opens contacts 201 to break the energizing circuit for relay 205 which opens its contacts 208 with resultant discontinuance of the D. C. field on the pump stator. I v

, Deenergization of relay 200 closes its back contacts 220, and since the cam 212 has at the same time closed switch 221 this completes an energizing circuit for a relay 222 through the normally closed contacts 223 of; a' switch 225 controlled by earn 213. Energizing of relay 222 closes its contacts 226 to apply the full D. C. field, i. e., stronger than normal, to both the pump stator 44 and control stator 45, thus immediately applying a strong Braking force on both of the rotors 75 and 85 to cause correspondingly prompt shifting of valve to supply the output of both pumps to the control cylinder and shifting of valve to its full increase pitch position with a strong pumping action.

These operating conditions continue only for the interval determined by the cam '213, and during approximately the last of its rotation, it shifts the switch 225 to open its contacts 223 and close its other pair of contacts 227. This breaks the energizing circuit for relay 222 which opens its contacts 226 to discontinue the D. C. field to both stators. At the same time, closing of switch contacts 227 completesan energizing circuit for the additional relays 230, and 231, through the back contacts 232 of relay 207. Closing of relay 230 results in the closing of its contacts 233 to apply a reverse A. C. field to the pump stator 44, and closing of relay 231 closes its contacts 234 to apply a reverse A. C. field to the control stator 45. This action is essentially the same as the operation under similar conditions described in connection with Fig. 12 and continues for the remainder of the interval determined by timer 210 until the propeller is fully feathered. Upon conclusion of the timed interval, all of switches 174, 221 and 227 open to shut off the electrical power to the system.

Unfeathering with the system of Fig. 13 is initiated by closing and temporarily holding closed the pushbutton switch 185. This energizes relay 207 to close its contacts 235 and complete an energizing circuit for relay 230, thus closing its contacts 233 and reapplying the reverse A. C. field to the pump stator 44. At the same time, the contacts 236 of relay 207 close to complete an energizing circuit for relay 200, since the contacts 216 have already been closed by deenergizing of relay 215 upon completion of feathering. Relay 205, however, remains open through the contacts 206 to keep its contacts 208 open and prevent reestablishing of the D. C. field to the pump stator.

Under these conditions, the pump rotor is positively driven to supply the necessary pressure fluid for cylinder 35, and the control rotor is similarly driven in the direction to shift valve 120 to its decrease pitch position. After initial shift toward operativepitch position, the propeller starts to rotate by wind-milling, and the switch can then be released to deenergize relay 207. The contacts 235 accordingly open to break the energizing circuit for relay 230 which thus opens its contacts 233 to discontinue the reverse A. C. field on the pump stator. At the same time, the back contacts 206 of relay 207 will close to establish the energizing circuit forrelay 205, thereby closing its contacts 208 to reapply the normal 7 D. C. field to the pump stator, thus completing reestablishment of normal operating conditions.

It will accordingly be seen that with either of these electrical systems, the control of the present invention provides for accurate adjustment of the pitch of the propeller with relation to a master speed source which can be varied as desired by the pilot in accordance with engine speed, and tests indicate that this control can be maintained within exceedingly close limits over an engine speed range as great as from 1500 to 2600 R. P. M. In addition to this highly accurate degree of adjustment afforded by the invention, the control assembly as described has the important practical advantages that it requires no moving or rotating oil seals or collector ring assemblies, since the hydraulic system is self-contained and since transmission of the electrical power is entirely by induction from stationary parts of the assembly to the rotating parts, and at the same time, it adds very little in the way of power requirements to the normal power load of the airplane.

The control apparatus of the invention is as effective for feathering and unfeathering as for pitch control under normal flight conditions, and it is also readily provided with safety means to counteract various types of control failure. Thus if the blades are not counterweighted, in the event of complete loss of pressure, the blades will go to their low pitch condition under the action of centrifugal blade torque. At the same time, it should be noted that the construction and arrangement of the mechanism as disclosed are such that either loss of fluid or serious pump failure are highly unlikely. Also the pitch control valve can be provided with spring loading to move this valve to either the high pitch or low pitch position in case of failure of the A. C. supply to the control field, as indicated at 240 in Fig. 11, and choice of which condition is preferable as between high or low pitch is primarily a function of the operational characteristics of the aircraft on which the propeller is installed.

The control of the invention also has special advantages as applied to multi-propeller airplanes. Thus Fig. 14 shows diagrammatically an arrangement in accordance with the invention for an airplane having a pair of propellers 250 and 251. Each of these propellers is accordingly provided with its own control system 252 and 253 respectively, which may be wired as shown in either of Figs. 12 and 13, but the A. C. power supply for both systems will be derived from the same generator 152. Thus with this arrangement, not only can each propeller be controlled individually as to pitch with relation to the rotating control field, but this control will extend also to the phase relationships of the propellers, with the result that both propellers operate not only at the same speed but also will be in the same phase relationship under normal operating conditions. The system is obviously applicable in the same way to any desired number of propellers controlled from the same generator.

While the forms of apparatus herein described constitute a preferred embodiment of the invention, it is to be understood that the invention is not limited to these precise forms of apparatus, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.

What is claimed is:

1. In a controllable pitch propeller having a rotary hub, a blade adjustably supported on said hub, power actuating means carried by said hub for eifecting adjustment in the pitch angle of said blade, a pump carried by said hub for developing hydraulic power for supply to said power actuating means, a magnetically responsive pump drive element within said hub, a magnetically responsive fluid pressure control element within said hub, means outside said hub for producing electromagnetic fields effective upon each of said magnetically responsive elements respectively, and means for controlling said fields to control the development and application of said fluid pressure with resultant control over the operation of said propeller.

2. In a controllable pitch propeller having a rotary hub, a blade adjustably supported on said hub, power actuating means carried by said hub for effecting adustment in the pitch angle of the blade, a pump carried by said hub for developing hydraulic power for supply to said power actuating means, a magnetically responsive 1 pump drive element'within said hub, a magnetically responsive fluid pressure control element within said hub, means mounting said elements respectively for rotation relative to said hub, means outside said hub for producing a magnetic field eifective upon said pump drive element to cause rotation thereof at a speed different from that of said hub to drive said pump for supplying fluid pressure, and additional means outside said hub for producing a magnetic field eifective upon said fluid pressure control element to control the application of said fluid pressure to said power actuating element with resulting control of the speed of rotation of said propeller.

3. In a controllable pitch propeller having a rotary hub, a blade adjustably supported on said hub, power actuating means carried by said hub for effecting adjustment in the pitch angle of the blade, a pump carried by said hub for developing hydraulic power for supply to said power actuating means, a magnetically responsive pump drive element within said hub, a magnetically responsive fluid pressure control element within said hub, means responsive to the position of said control element relative to said hub for controlling the application of fluid pressure to said power actuating means to control the speed of the propeller, means outside said hub for producing a magnetic field effective upon said pump drive element to cause rotation thereof at a speed different from that of said hub with resultant driving of said pump, and additional means outside said hub for producing a magnetic field rotating at a predetermined speed and efiective upon said fluid pressure control element to cause rotation thereof at the same speed with corresponding .regulation of the speed of said propeller.

4. In a controllable pitch propeller having a rotary hub, a blade adjustably supported on said hub, power actuating means carried by said hub for elfecting adjustment in the pitch angle of'said blade, a pump carried by and rotatable with said hub for developing fluid pressure for supplying to said power actuating means, a pump drive element on said hub for driving said pump in response to relative rotation therebetween, said pump drive element being magnetically responsive, and means outside said hub for developing a magnetic field effective upon said drive element to produce a diflerential between the speed of rotation of said element and that of said hub causing the driving of said pump.

5. In a controllable pitch propeller having a rotary hub, a blade adjustably supported on said hub, power actuating means carried by said hub for effecting adjustment in the pitch angle of said blade, a pump carried by and rotatable with said hub for developing fluid pressure for supply to said power actuating means, a pump drive element on said hub for driving said pump in response to relative rotation therebetween, said pump drive element being magnetically responsive, and means outside said hub fordeveloping a direct current magnetic field effective upon said drive element to produce a differential between the speed of rotation of said element and that of said hub to cause the driving of said pump.

6. In a controllable pitch propeller having a rotary hub, a blade adjustably supported on said hub, power actuating means carried by said hub for effecting ad justment in the pitch angle of said blade, a pump carried by said hub for developing fluid pressure for supply to said power actuating means, a pump drive element on said hub for driving said pump in response to relative rotation therebetween, said pump drive element being magnetically responsive, and means outside said hub for developing a counter-rotating magnetic field effective upon said drive element to retard its speed of rotation below that of said hub to cause the driving of said pump.

7. In a controllable pitch propeller having a rotary hub, a blade adjustably supported on said hub, power actuating means carried by said hub for effecting adjustment in the pitch angle of said blade, a pump carried by said hub for developing fluid pressure for supplying to said power actuating means, a pump drive element on said hub for driving said pump in response to relative rotation therebetween, said pump drive element being magnetically responsive, and means outside said hub for subjecting said drive element to a non-rotating magnetic field to retard the rotation of said element relative to said hub to cause the driving of said pump.

8. In a controllable pitch propeller having a rotary hub, a blade adjustably supported on said hub, power actuating means carried by said hub for effecting adjustmentin the pitch angle of said blade, a pump carried by said hub for developing fluid pressure for supply to said power actuating means, a pump drive element on said hub for driving said pump in response to relative rotation therebetween, said pump drive element being magnetically responsive, and means outside said hub for producing a field rotating in the direction opposite to the rotation of said hub to cause the driving of said pump.

9. In a controllable pitch propeller having a rotary hub, a blade adjustably supported on said hub, power actuating means carried by said hub for eifecting adjustment in the pitch angle of said blade, a pump carried by said hub for developing fluid pressure for supply to said power actuating means, a pump drive element on said hub for driving said pump in response to relative rotation there- 15 between, said pump drive element being magnetically responsive, means outside said hub for subjecting said drive element to a non-rotating magnetic field to retard the rotation of said element relative to said hub to cause the driving of said pump, and additional means for subjecting said drive element to a magnetic field rotating in the reverse direction to cause the driving of said pump.

References Cited in the file of this patent UNITED STATES PATENTS 2,403,243 Seppeler July 2, 1946 FOREIGN PATENTS 503,154 Great Britain Apr. 3, 1939 

